Aspect Particles Decision Flowchart

A decision tree for 了, 过, 着, and 在

Chinese verbs don't conjugate. There is no walked / walks / will walk. The verb 走 shows up identically whether you walked yesterday, are walking now, or plan to walk tomorrow. This is the first thing that trips up English-speakers, and the second thing is the reflex to fix it by sprinkling aspect particles everywhere. Don't. Aspect is not tense.

English encodes when on the verb. Chinese leaves when to adverbs and context, and uses particles to mark something different: what kind of situation the action is in. Did it complete? Did it change something? Is it ongoing? Did it ever happen? Those are aspect questions, and four little particles answer them.

// Tense (English) encodes time on the verb:
type EnglishVerb = {
    past:   "walked",
    present:"walks",
    future: "will walk"
};

// Aspect (Chinese) leaves the verb alone and tags the situation:
interface Situation {
    verb:       "走";                       // never changes
    completed?: "了";                       // action finished / state changed
    experienced?:"过";                      // ever happened, at least once
    stative?:   "着";                       // ongoing state resulting from verb
    inProgress?:"在" | "正在";              // action happening right now
}

The four fields are optional and roughly mutually exclusive at any given moment. Pick at most one. Most of your sentences will pick none — habitual statements, future plans, and general truths take no aspect particle at all. That's the other reflex to unlearn: particles aren't decoration. Every one of them means something specific, and using them where they don't belong is a bug.

1. The four particles at a glance

Pin this table somewhere. The rest of the article expands on it, but this is the whole type system in one grid.

Position is not cosmetic — it's how the parser tells them apart. 在 sits before the verb because it's framing the action as ongoing. 了, 过, and 着 sit after the verb because they comment on what the verb did or produced. Sentence-final 了 is a separate beast with its own rules; we'll get to it.

2. The decision tree

When you want to describe something that's happening or happened, walk these questions top to bottom. The first "yes" picks your particle. If you get to the bottom with no yes, you use no particle.

// aspectOf(situation): Particle | null

if (situation.happeningRightNow)         return "在";   // Q1
if (situation.completedOrChanged)        return "了";   // Q2
if (situation.everHappenedInLife)        return "过";   // Q3
if (situation.stateResultingFromVerb)    return "着";   // Q4
return null;                                        // habitual / future / general

Q1 — Is the action in progress right now?

If you could point at someone and say "look, they're doing it," that's 在 territory. Place it before the verb. 正在 is the emphatic version — "right this minute, actively" — and is interchangeable with 在 for most practical purposes.

我在看书。         wǒ zài kàn shū        — I am reading (a book).
他正在睡觉。       tā zhèngzài shuì jiào — He is sleeping right now.
我们在吃饭呢。     wǒmen zài chī fàn ne  — We're eating. (呢 softens it.)

Q2 — Did the action complete, or did a state change?

If the action finished, or something transitioned from one state to another, use 了. Place it directly after the verb for completion of a specific action; place it at the end of the sentence for a state change that affects the whole situation.

我吃了饭。         wǒ chī le fàn         — I ate (completed the meal).
下雨了。           xià yǔ le             — It's (started) raining. — state change
他高了。           tā gāo le             — He's grown taller. — state change

Q3 — Has this ever happened, at some unspecified past?

If you're reaching for a life-experience stamp — "I've done X at some point" — use 过. It's the resume bullet point of aspect: it asserts the experience exists in your history, without locating when.

我去过北京。       wǒ qù guo Běijīng     — I've been to Beijing.
你吃过寿司吗？     nǐ chī guo shòusī ma  — Have you ever eaten sushi?
我没看过这个电影。 wǒ méi kàn guo ...    — I haven't seen this movie.

Q4 — Is something in a state because of the verb?

Not the action itself, but the state it leaves behind. 着 marks the lingering, stative consequence. If someone opened a door and the door is now sitting open, that's 开着. If someone put a book on a table and it's now lying there, that's 放着.

门开着。           mén kāi zhe           — The door is open (left open).
他站着说话。       tā zhàn zhe shuō huà  — He speaks while standing.
桌子上放着一本书。 zhuōzi shàng fàng zhe yì běn shū — A book lies on the table.

Q5 — None of the above

No particle. This is the default. Habitual actions, future plans, general statements, descriptions, preferences — none of them take aspect marking. The particle-less sentence is not incomplete; it's correct.

我每天七点起床。   wǒ měi tiān qī diǎn qǐ chuáng — I get up at 7 every day.
我喜欢咖啡。       wǒ xǐhuan kāfēi               — I like coffee.
明天我去上海。     míngtiān wǒ qù Shànghǎi       — Tomorrow I go to Shanghai.

3. 了 is the hardest

If you fail on one particle, it will be 了. It wears two hats and beginners conflate them. Hat one: verbal 了 — placed right after the verb, marks that the action completed. Hat two: sentential 了 — placed at the end of the sentence, marks a change of state at the situation level. The two can co-occur. Let's walk ten examples.

// 1. Verbal 了 — action completed, specific object.
我吃了三碗饭。       wǒ chī le sān wǎn fàn
                    — I ate three bowls of rice.

// 2. Verbal 了 — completion, short clause.
他买了一本书。       tā mǎi le yì běn shū
                    — He bought a book.

// 3. Sentential 了 — state change: it wasn't raining, now it is.
下雨了。             xià yǔ le
                    — It's (started) raining.

// 4. Sentential 了 — state change: he was short, now he's taller.
他高了。             tā gāo le
                    — He's grown taller.

// 5. Sentential 了 — change: I wasn't hungry before; now I am.
我饿了。             wǒ è le
                    — I'm hungry (now).

// 6. Double 了 — action completed AND the resulting state is relevant now.
我吃了饭了。         wǒ chī le fàn le
                    — I've already eaten. (I'm fed, don't feed me.)

// 7. Negative — 没 replaces 了 entirely. Never "没...了".
我没吃饭。           wǒ méi chī fàn
                    — I didn't eat / haven't eaten.

// 8. Habitual — one-time 了 is wrong here. No particle.
我每天七点起床。     wǒ měi tiān qī diǎn qǐ chuáng
                    — I get up at 7 every day.

// 9. One-time past — 了 is correct; it's a completed event.
我昨天七点起床了。   wǒ zuótiān qī diǎn qǐ chuáng le
                    — Yesterday I got up at 7.

// 10. Future plan — no 了. Use 会 for intention, or let time-word do it.
明天我去北京。       míngtiān wǒ qù Běijīng
                    — Tomorrow I'm going to Beijing.

4. 过 vs 了 — the ever-vs-just-did distinction

Both particles live in the past-ish zone, and both sit after the verb, so beginners swap them. The difference is about what the sentence is claiming.

我去了北京。         wǒ qù le Běijīng
                    — I went to Beijing. (Specific trip. Probably recent.)

我去过北京。         wǒ qù guo Běijīng
                    — I've been to Beijing. (At some point in my life.)

我吃了饺子。         wǒ chī le jiǎozi
                    — I ate dumplings. (Today. Just now. At that meal.)

我吃过饺子。         wǒ chī guo jiǎozi
                    — I've eaten dumplings before. (Yes, I know what they are.)

A useful heuristic: if the English translation is comfortable with "I've ever..." or "I've... before," use 过. If it's comfortable with a specific past-tense action and a specific occasion, use 了.

5. 着 — the stative

着 is the least common of the four in beginner speech, but it's essential for description. It takes a verb and freezes it into the resulting state. The action is done; the configuration persists.

他站着。             tā zhàn zhe
                    — He is standing (in the standing state).

门开着。             mén kāi zhe
                    — The door is open (has been opened, stays open).

她穿着红衣服。       tā chuān zhe hóng yīfu
                    — She's wearing a red shirt (wearing-state).

桌子上放着一本书。   zhuōzi shàng fàng zhe yì běn shū
                    — A book is lying on the table.

A common use is the serial pattern verb1 着 + verb2, which describes the first verb as the ongoing backdrop to the second:

他站着说话。         tā zhàn zhe shuō huà
                    — He speaks while standing.

她笑着看我。         tā xiào zhe kàn wǒ
                    — She looks at me, smiling.

6. Common mistakes

7. Ten annotated sentences

One of each, plus a few edge cases. The comment above each line tags the aspect and the reasoning.

// [在] in-progress, happening now.
我在写代码。         wǒ zài xiě dàimǎ
                    — I'm writing code.

// [正在] emphatic in-progress; active, right this second.
他正在开会。         tā zhèngzài kāi huì
                    — He's in a meeting right now.

// [了, verbal] single completed action.
我看了那部电影。     wǒ kàn le nà bù diànyǐng
                    — I watched that movie.

// [了, sentential] state change — it got cold.
天冷了。             tiān lěng le
                    — The weather's turned cold.

// [了 + 了] completed AND currently relevant.
我写了报告了。       wǒ xiě le bàogào le
                    — I've finished the report (and it's done, current state).

// [过] life experience, unspecified time.
我学过日语。         wǒ xué guo Rìyǔ
                    — I've studied Japanese (before, at some point).

// [过, negative] never experienced.
我没去过日本。       wǒ méi qù guo Rìběn
                    — I've never been to Japan.

// [着] resulting state.
灯开着。             dēng kāi zhe
                    — The light is on.

// [着 + main verb] ongoing backdrop + foreground action.
他听着音乐工作。     tā tīng zhe yīnyuè gōngzuò
                    — He works while listening to music.

// [none] habitual — no particle.
我每天喝咖啡。       wǒ měi tiān hē kāfēi
                    — I drink coffee every day.

8. Edge cases

A few situations that don't fit the tree cleanly, but you'll hit them early:

• Sequenced past actions. When you narrate a sequence of completed events (I got up, brushed my teeth, left the house), verbal 了 often appears only on the last verb, or on none — the past framing is carried by context. Over-marking each verb with 了 sounds robotic.
• "Soon" / imminent change. 要...了 frames an imminent event: 要下雨了 (it's about to rain). This is a dedicated construction; the 了 here is the sentence-final change-of-state flavor, anticipating the change.
• Duration + 了. 我在这里住了三年 (I've lived here three years) uses verbal 了 to mark the duration accumulated. Add sentence-final 了 (住了三年了) to say "and I still live here" — the state persists.
• 没 instead of 不. Aspect negation uses 没, not 不. 不 negates habits and intentions; 没 negates completed or experienced actions. 我不吃肉 (I don't eat meat, ever) vs 我没吃肉 (I haven't eaten / didn't eat meat).

9. Next steps

The tree is a starting point, not the whole grammar. 了 especially has book-length treatments in linguistics literature. For practical use, these are the natural follow-ups:

• Daily routines — aspect particles in the context of everyday schedules
• Weather talk — sentence-final 了 earns its keep describing the sky
• Module 3: State Management — the full curriculum on aspect
• Flashcard review — lock in the four particles via spaced repetition

Once the tree is automatic, you stop translating English tenses into Chinese. You start asking the aspect question directly: did this finish, did this change, is this ongoing, did this ever happen. That shift is the whole point of Module 3.